1. Field of the Invention
The present invention relates to an electrostatic precipitator, and more particularly, to an electrostatic precipitator, in which a photo-catalyst technology is utilized for sterilization and deodorization.
2. Discussion of the Related Art
In general, the electrostatic precipitator collects and removes solid state, and liquid state particles floating in a gas. FIG. 1 illustrates a section of a background art electrostatic precipitator, with reference to which the background art electrostatic precipitator will be explained.
The background art electrostatic precipitator is provided with a body 10 having an intake grill 12 and a discharge grill 14, and filters 20, 30, and 100 and fan 16 mounted inside of the body 10. In the filters, there are a pre-filter 20 at rear of the intake grill 12 for primary filtering of dusts from intake air, an electrostatic precipitating part 100 at rear of the pre-filter 20 for electrical removal of dusts, deodorizing filter 30 at rear of the electrostatic precipitating part 100 for removal of odor in air.
The foregoing electrostatic precipitator will be explained in detail with reference to FIG. 2. The electrostatic precipitating part 100 is provided with the discharge unit 110 for charging dusts and the like in air, and the collecting unit 130 for collecting the dusts charged in the discharge unit 110. In detail, the body 10 has a discharge unit case 112 and holders 114 on both sides of the discharge unit case 112. And, there are a plurality of ground electrodes 116 fitted to the holders 114 at fixed intervals, and a plurality of discharge electrodes 118 between the ground electrodes 116. And, the body 10 has a collecing case 132 which has a plurality of collecting electrodes 134 fitted thereto at fixed intervals for acting as ground electrodes, and there are a plurality of positive electrodes 136 between the collecting electrodes 134. A plurality of projections 138 may be provided on top of both the collecting electrodes 134 and the positive electrodes 136 for maintaining a gap between the electrode plates 134 and 136. The collecting electrodes 134 and the positive electrodes 136 are conductors, such as conductive paint or aluminum foil. Resin of a good insulating property is coated or bonded on the conductors.
At time, there is a metal mesh(not shown) between a discharge unit 110 and a collecting unit 130 for minimizing electric field interference between the discharge unit 110 and the collecting unit 130.
In the meantime, there are a "-" voltage applying terminal 142 and a "+" voltage applying terminal 144; the "-" voltage applying terminal 142 is connected to the ground electrodes 116 in the discharge unit 110 and the collecting electrodes 134 in the collecting unit 130, and the "+" voltage applying terminal 144 is connected to the discharge electrodes 118 and the positive electrodes 136.
The operation of the background art electrostatic precipitator will be explained with reference to FIGS. 1 and 2.
Upon application of power to the electrostatic precipitator, the fan 16 is put into operation to cause outside air to flow into the body 10 through the intake grill 12. The air is primarily filtrated of comparatively large sized dusts as the air passes through the prefilter 20 and flows to the discharge unit 110. As the ground electrodes 116 and the discharge electrodes 118 in the discharge unit 110 are at application of voltage, a corona discharge occurred between the ground electrodes 116 and the discharge electrodes 118, charging dust particles flowed in the discharge unit 110. The dusts charged in the discharge unit 110 continues to flow toward the collecting unit 130, where, as the charged dusts are charged of "+", a repulsive force is acted between the dusts and the positive electrodes 136 having a "+" voltage applied thereto, and an attracting force is acted between the dusts and the collecting electrodes 134 having a "-" voltage applied thereto. Accordingly, the charged dusts are accelerated toward the collecting electrodes 134, being collected at the collecting electrodes 134 at last. The air, passed through the collecting unit 130 finally, is removed of odors in the air as the air passes through the deodorizing filter 30 of active carbon, to become clean air, which is discharge through the discharge grill 14. However, the background art electrostatic precipitator can not remove harmfull microbes contained in the air, and has a poor deodorizing performance, causing a problem that the harmful microbes are discharged into a room without being filtrated, or accumulated on electrode plates in the collecting unit 130 and decomposes to give out bad smell.
To cope with this problem, so called photo-catalyst technology is developed, in which a substance (hereafter called "photo-catalyst") adapted to be activated by a photo-energy to have sterilizing and deodorizing capability is used, of which typical photo-catalyst is titanium oxide TiO.sub.2. The photo-catalyst like titanium oxide has an excellent adsorption power to organic substances and is excited when exposed to a photo energy to form various forms of radical, which sterilizes microbes by a strong oxidation power and, on the same time, decomposes substances giving out bad smells in reaction with the radical.
This may be explained in detail referring to FIG. 3 as follows.
When a photo-energy emitted from an UV lamp and the like is directed onto a photo-catalyst, an electron in a valence band is transited to a conduction band, generating an electron and a hole. As these electron and hole have very strong oxidizing and reducing power, these electron and hole make reaction with water vapor H.sub.2 O or oxygen O.sub.2 in air, to produce active oxygens, such as OH radical, H radical, and super oxide n ion O.sub.2.sup.-. And, as these radicals have strong bonding forces to other components, these radicals break bonding of substances giving a bad smell, thereby making deodorization. That is, as OH radical breaks bonding of an organic substance which causes an odor and makes a direct bonding with the organic substance, leaving water vapor and carbon dioxide finally, the odor is removed. And, as OH radical has a strong oxidizing power which sterilizes microbes, OH radical can sterilize microbes. When the electron or hole make a direct bonding with organic substance, the direct bonding breaks bonding of the organic substance, changing the organic substance to another form of radical. And, the another form of radical breaks a bonding of another organic substance, to form water vapor and carbon dioxide at the end, thereby making deodorization. Thus, by proceeding the foregoing process, sterilization and deodorization can be made.
PCT application(PCT/US 96/14204) discloses a filter coated with a photo-catalyst and a UV lamp which activates the aforementioned photo-catalyst. However, the technologies on sterilization and deodorization using photo-catalyst known up to now have the following problems.
First, as a photo-energy is required for exciting a photo-catalyst as titanium oxide, a separate photo-energy source for generating such a photo-energy has been required additionally. That is, the UV lamp and the like used additionally as the photo-energy source increases components in the electrostatic precipitator, making the electrostatic precipitator to have a complicated structure and to cost high.
Second, the UV lamp or filter coated with photo-catalyst mounted in air stream make resistance to air flow, which causes a pressure loss of the air flow.